Sheet metal nut

ABSTRACT

A sheet metal nut having an inner threaded barrel portion connected to an outer, hexagonally shaped barrel portion by a connecting web adjacent one end of said barrel portions has an hexagonally shaped depression formed in the inner barrel portion over a limited axial extend thereof adjacent the connecting web. The internal faces of the hexagonal depression are disposed opposite to and match the hex wrenching faces on the outer barrel portion and are effective to transmit torque to the inner barrel portion when the nut is turned onto a mating bolt thereby reducing the torsional strain on the connecting web incident to tightening of the nut.

Unite States ate Duffy et al.

1*Mar. 12, 1974 SHEET METAL NUT [75] Inventors: William B. Duffy,Berkeley Heights;

Charles K. Fisher, Belford, both 0 [73] Assignee: TRW Inc., Cleveland,Ohio Notice: The portion of the term of this patent subsequent to May 2,1989, has been disclaimed.

[22] Filed: Jan. 17, 1972 [21] Appl. No.: 218,246

[52] U.S. Cl 85/32 R [51] Int. Cl. F16b 37/02 [58] Field of Search 85/32R; 151/38 [56] References Cited UNITED STATES PATENTS 3.659.491 5/1972Duffy et al 151/38 Primary Examiner Marion Parsons, Jr.

momaffigeni, a; Firfii j aniegTKI O CESnnOr; Hall & Houghton [5 7]ABSTRACT A sheet metal nut having an inner threaded barrel portionconnected to an outer, hexagonally shaped barrel portion by a connectingweb adjacent one end of said barrel portions has an hexagonally shapeddepression formed in the inner barrel portion over a limited axialextend thereof adjacent the connecting web. The internal faces of thehexagonal depression are disposed opposite to and match the hexwrenching faces on the outer barrel portion and are effective totransmit torque to the inner barrel portion when the nut is turned ontoa mating bolt thereby reducing the torsional strain on the connectingweb incident to tightening of the nut.

3 Claims, 9 Drawing Figures SHEET METAL NUT CROSS-REFERENCE TO RELATEDAPPLICATION This application relates to our copending application, U.S.Ser. No. 121,636, filed Mar. 8, 1971, now U.S. Pat. No. 3,659,491,issued May 2, I972. The claims appended to this application are,however, patentably distinct from those of the said copendingapplication and said Patent. Both applications and said Patent areassigned to a common assignee, to wit, TRW Inc.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to coupled nut and washer assemblies, particularly assemblies ofthe type wherein the nut is of sheet metal construction and thecomponents of the assembly are freely rotatable relative to one another.

2. Description of the Prior Art The prior art includes numerouspreattached or preassembled nut and washer assemblies. In the earlierart one finds disclosures of integral nut and washer combinations andassemblies wherein the components are separately fabricated butnonrotatably coupled. Characteristic of the foregoing devices is thedisclosure of U.S. Pat. No. 2,761,349 (R. M. Heller) whereincombinations and assemblies of both sheet metal and headed componentsare depicted. While integral and fixed assemblies of the typeexemplified by Heller have made a recognized contribution to the artwith respect to convenient handling by the user, simplification ofpackaging and shipping as compared with separate nuts and washers,reduction of the loss of washers to be used with nuts in giveninstallations, and effective insurance that the proper size and shape ofwasher is consistently available for use in a specified application; ithas likewise been recognized that in applying such parts to cooperatingbolts or studs and tightening same against a workpiece surface,excessively high torque must be applied to the nut to achieve a desiredtension on the bolt or stud in that continuous simultaneous rotation ofthe nut and washer, subsequent to engagement of the workpiece by thewasher, precipitates a markedly increased resistance to turning of thenut and thus an extremely rapid and highly undesirable applied torqueincrease. In addition, the edge of the washer scores and often gouges orcuts a groove in the confronting workpiece surface and the increasingresistance to rotation creates problems with respect to the peeling,rupturing and deforming of sealing elements when such elements aredisposed adjacent the undersurface of the washer.

Having recognized the aforementioned deficiencies in integral or fixedassemblies, designers later moved to eliminate same through thedevelopment of combinations wherein the washer element was capable ofrotation relative to the nut and wherein the latter component could beheaded or sheet metal construction and carry either a multiconvolutionthread of a standard type or a single helix thread engager, or a threadcutting or forming element for engaging an unthreaded stud. U.S. Pat.Nos. 2,943,661 (W. Stern) and 2,851,079 (R. M. Heller) and British Pat.No. 929,807 (United-Carr Fastener Corporation) contain pertinentdisclosures to which reference may be had for a clearer understanding ofthe advantages to be derived from combinations wherein the componentsare relatively rotatably coupled. Notwithstanding the fact that the lastmentioned Heller and Stern and United-Carr F astener disclosures placedparticular emphasis on the merits of rotatable combinations with respectto the minimization of the risk of deformation or other damage tosealing means employed in conjunction with the parts disclosed therein,the fast remains that the extent to which that objective was realizedwas primarily attributable to the capacity of the disclosed nuts torotate independently of any coincident rotation of the washer subsequentto initial clamping engagement of the washer with the confrontingsurface of a workpiece. However, regardless of the presence or absenceof a sealing element, the principal objective sought to be achieved inthe construction of rotatably coupled nut and washer assemblies is thereduction of the torque which must be applied to the nut to realize aspecified degree of tension on a bolt, screw or stud, etc., onto whichthe nut is turned. Thus it follows that a construction, particularlywith regard to the nut to washer connection, which renders thecomponents free spinning relative to one another and greatly reduces thepossibility of any continuing washer rotation subsequent to initialclamping of the washer against a workpiece surface, not only providesfor greatly improved torquetensile relationship in the fastenerapplication but also even further minimizes the potential for sealerdeformation, even in situations wherein the bond between the sealingelement and the washer is weak or the sealing element per se isstructurally defective.

The principal motivating force behind the development of the presentlydisclosed device was to realize the aforementioned critical objectivethrough an improved rotatably coupled sheet metal nut and washerassembly. The extent to which that purpose has been accomplished can beappreciated by way of a more detailed inspection of the aforementionedpatents when considered in the light of the description of a preferredembodiment of the improved assembly which follows hereinafter.

SUMMARY OF THE INVENTION A fastener assembly of the type wherein a sheetmetal nut having inner and outer barrel portions is rotatably assembledwith an apertured lock washer. The outer nut barrel portion includes aperipheral skirt which rotatably bears on the washer adjacent theaperture therein. The assembly is particularly characterized by animproved nut to washer connection including a connecting collar on theinner nut barrel portion which is curled under the internal edge of theaperture in the washer, the washer having a recessed undersurface inwhich portions of the connecting collar are seated, and a peripheralbearing ring on the inner nut barrel portion disposed adjacent theconnecting collar and the washer aperture. The said bearing ring isformed from metal skived from the inner nut barrel portion and compactedinto the ring configuration. The bearing ring has a smooth undersurfacedisposed at a selectively predetermined angle to the longitudinal axisof the nut and the washer has a smooth surface adjacent the aperturetherein, which latter surface is complementary to and in confrontationwith the undersurface of the bearing ring. Thus, the connecting collarand bearing ring cooperate to maintain the nut and washer in an assemblywherein the said components are free spinning relative to one another.The said construction is particularly adapted to provide an improvedtorquetensile relationship in effecting a coupling wherein said fastenerassembly is turned onto a cooperating male fastener element protrudingthrough an apertured member and the washer is tightened against theconfronting surface of the member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a nut andwasher assembly according to the invention;

FIG. 2 is a side elevational view of the assembly depicted in FIG. I;

FIG. 3 is an enlarged view of a cross section taken on line 3-3 of FIG.1;

FIG. 4 is a view of the invention similar to FIG. 3 as applied to acooperating bolt to secure two overlapping apertured members which aredepicted fragmentarily and in cross section;

FIG. 5 is an enlarged transverse cross-sectional view of the washercomponent;

FIG. 6 is a further enlarged view of the right side of FIG. 3 depictingthe improved nut to washer connection;

FIG. 7 is an enlarged side elevational view of a slightly modifiedembodiment of the washer component;

FIG. 8 is a plan view of a modified form of a nut and washer assemblyaccording to the invention; and

FIG. 9 is an enlarged view ofa cross section taken on line 9-9 of FIG.8.

DESCRIPTION OF A PREFERRED EMBODIMENT A relatively rotatable nut andwasher assembly according to the invention includes a nut 2 drawn fromsheet metal and having an inner barrel portion 4 connected at its upperend through a web 6 to an outer, hexagonally shaped barrel portion 8which circumscribes the inner barrel portion in spaced relationshipthereto, and a frusto-conically shaped, spring lock washer 10 which isrotatably coupled to the lower end of the inner barrel portion 4 of thenut.

The lower end of the outer nut barrel portion 8 includes a radiallyextending peripheral skirt 16 having a smooth undersurface 18 which iscomplementary to and, in the assembly, rotatably bears on the upperconvex surface 20 of the washer 10. The inboard wall of the inner nutbarrel portion 4 carries a multiconvolution thread 22 of a standard typewhich is adapted for threaded engagement with a cooperating bolt.Adjacent its lower end, the outboard wall 24 of the said inner barrelportion carries a peripheral bearing ring 26. The bearing ring 26 isformed from metal skived from the outboard wall 24 and compacted intosaid ring configuration during fabrication of the nut. Further, thebearing ring has a generally triangular configuration as is clearly seenin the cross-sectional views of FIGS. 3, 4 and 6 and also has a smooth,nonburred undersurface 28 disposed at a selected acute angle to thelongitudinal axis of the nut. The surface 28 is ideally,

but not necessarily, at an angle on the order of 45 to the longitudinalaxis of the nut or an engaged bolt in that tests have indicated that,when the said undersurface is disposed at an acute angle substantiallyless than 45, the frictional resistance to tightening of the nut on abolt rises appreciably in that the confronting complementary surface ofthe washer to be described hereinafter tends to clamp or jam the innernut barrel against the bolt shank to an excessive degree in what mightbest be described as a collet effect. Immediately adjacent and below thebearing ring 26, the said inner barrel portion terminates in aconnecting collar 30 which,

subsequent to nut formation and prior to coupling wit the washer, liesgenerally parallel to the aforementioned nut axis.

As best seen in FIG. 5, the frusto-conical spring lock washer 10 has acentral through aperture 32, a generally cylindriform lip 34 projectingupwardly from its convex surface 20 adjacent the aperture 32 and arecess 36 formed in its under or concave face adjacent the saidaperture. The inboard surface 38 of the lip 34 has a downwardlytapering, funnel-like configuration and the recess 36 has a generallycorresponding but inverted funnel shape and the said respective lip andrecess surfaces intersect in a very thin circumferential rim 40 which ineffect defines the minor diameter of the aperture 32.

In effecting the assembly of the washer 10 to the nut 2, the initiallycoaxial roller 30 is inserted into the aper ture 32 in the washer andthereafter flared outwardly whereby its terminal end is loosely curedunder the circumferential rim 40 and nested in the recess 36. Thus, theundersurface 18 of the skirt 16 is brought to bear against a localizedarea of the convex face 20 of the washer (said area being generally butnot necessarily always less than one-half the total area of said convexface), and the complementary smooth surfaces 28 and 38 of the bearingring and washer lip, respectively, are also placed in opposed orconfronting relationship. While the aforementioned nut to washerconnection is relatively loose to permit free spinning of the componentsrelative to one another, the connection is likewise effective tomaintain the components in assembly under normal conditions of usage, towit, during packaging, shipping and repeated applications to and removalfrom a cooperating bolt.

By having particular reference to FIG. 6, the reader will observe whatis considered to be an ideal nut to washer connection, i.e., one whereinthe nut skirt is in contact with the opposing surface of the washer butthere are slight gaps, on the order of.OlO inch, between the surfaces 28and 38 of the bearing ring and washer, respectively, and .005 inchbetween the opposing portions of the collar 30 and the recess 36. Testsconducted to date indicate that the maintenance of the aforementionedspacing insures a freely rotatable combination and, what is equallysignificant, insures that the skirt 16 of the nut is always in contactwith the confronting washer surface to provide at least a minimal biasof the washer toward the engaged surface of a workpiece and effect aresultant locking tension on a cooperating bolt in a joint whereinrelatively low torque is applied to the nut incident to preliminary oreven final specified torquing of the nut.

In a typical joint such as that depicted in FIG. 4, the improvedfastener assembly is applied to the shank of a threaded bolt 42 tosecure a first apertured member 44 to a second apertured member 46wherein the latter is usually the fixed or base member in the joint.When the nut is turned onto the bolt to the point where the head 48 ofthe bolt is drawn against the remote surface 50 of the second member 46and the lower peripheral washer edge is pressed against the proximatesurface 52 of the first member 44 under relatively minimal clampingpressure or bias exerted on the washer by the nut skirt, the washerthereupon ceases further corresponding rotation with respect to the nutor the engaged members surface 52 and independent rotation of the nutmay be continued until the specified degree of torque has been appliedthereto, as dictated by the tightness desired in the joint, the grade ofbolt utilized and other variable factors which will be obvious to thosefamiliar with the art. As may be readily observed from a comparison ofFIGS. 3 and 4, continued turning of the nut onto the bolt, absent anyfurther washer rotation, precipitates a discrete flattening of thespring lock washer due to the pressure exerted thereon by the skirt l6,and thus the washer exerts a reverse axial tension on the nut to lockthe interengaged nut and bolt threads in the well-known manner. Further,since only the nut component rotates during tightening of the joint, theamount of torque which must be applied to the nut to achieve the desiredtension on the bolt is substantially reduced. To put it in other words,during tightening there is negative development of false or unnecessarytorque which would otherwise result from coincident rotation of thewasher against the confronting surface 52 of the member 44. From a stillcloser inspection of FIG. 4, one will observe that the progressive buildup of tension in the joint incident to the application of ultimatetightening torque to the nut exerts an axial pull on the inner nutbarrel which yields down wardly to close the gap between the bearingring and washer and precipitates a consequent clamping of theconfronting washer surface 38 against the opposed surface 28 of thebearing ring. Even after these surfaces are placed in contact and thebearing ring surface is rotating against the washer, the smooth,complementary configuration of the opposed surfaces permits continuedunimpeded rotation of the nut with only negligible, if any, increase inthe torque required to overcome the minimal increase in rotationresisting friction. Moreover, the presence of the bearing ring in thecombination prevents the inner nut barrel from being pulled through thewasher aperture as the barrel yields downwardly responsive to thetension build up described above, and, what is equally if not moreimportant, the clamping of the washer against the bearing ring transfersa compressive force from the flattened spring washer directly to thelower end of the inner nut barrel whereby the said barrel end is urgedinwardly and the nut thread embraces both the upper and lower faces ofthe mating bolt thread. When the nut is torqued up to the point wherethe mating bolt is approaching its ultimate tensional strength, theaforementioned inward pressure on the nut barrel provides for aneffective and improved locking and resistance to loosening of thecomponents in the joint. Thus, the bearing ring 26 prov ides for theeffective transfer of at least a portion of the reactive tensional forcefrom the compressed spring washer directly to the inner nut barrel andthe engaged threads and contributes a functional improvement in jointsof the type disclosed, particularly wherein sheet metal components areutilized. In fact, tests conducted to date indicate that, regardless ofthe amount of torque required to generate a desired amount of tension ina mating bolt, the ultimate tension which can be derived isapproximately doubled when the bearing ring is present at an angle ofapproximately 45, as compared with an assembly wherein the inner nutbarrel does not embody a bearing ring or equivalent element. It shouldalso be noted that while the surface 28 of the bearing ring was earlierdescribed as being at a selected acute angle to the longitudinal nutaxis, the said surface may not necessarily be straight, but rather maybe slightly convex while the surface 38 of the washer may becomplementarily convex, whereby frictional resistance to relativerotation is further obviated.

FIG. 7 depicts a slightly modified washer 10a which includes a pluralityof spaced projections or teeth 54 depending from the undersurfacethereof, which projections or teeth are particularly adapted for bitingengagement with the surface of a metallic mounted member to effect anelectrical ground where required. The same projections or teeth willalso afford additional resistance to washer rotation during nuttightening.

By again having reference to FIGS. 3 and 4, the reader will also readilyappreciate that, as compared with an assembly of a headed nut devoid ofa peripheral skirt and a rotatable washer, the skirt of the sheet metalnut of the present invention provides a barrier between the convexwasher surface 20 and the leading end of a power driver chuck. Ergo,when such a tool is utilized to tighten a nut, the skirt inhibitsundesirable scoring or marring of the washer finish beyond theperipheral edge of the nut skirt.

The modified embodiment of the invention depicted in FIGS. 8 and 9, isessentially the same as that earlier described, particularly withreference to the nut to washer connection. Further, the modified form isdesigned to function in the same manner in cooperation with a bolt in ajoint and may carry the alternate type of toothed lock washer depictedin FIG. 7. However, in adapting the invention to accommodate largersizes of bolts, i.e., bolts on the order of 1/4 inch diameter or larger,it was observed that during final tightening wherein the ultimatetensional strength of the bolt was being approached, it became somewhatdifficult to deliver the torque required to rotate the inner nut barrelthrough the wrenching faces of the outer hex barrel and the outer barrelfrequently sheared away from the tubular inner barrel at the connectingweb. Responsive to further experimentation, it was discovered that theaforementioned problem in larger sizes could be negated by providing ahex-shaped depression 56 in the upper end of the inner nut barrel 4bduring the process of nut formation and prior to the tapping of the saidbarrel. There are several reasons why the formation of the hexdepression 56 is seen to strengthen the nut and increase its torsionalresistance to shearing at the web. To begin with, one will readilyappreciate that the compacting of the metal, incident to depressionformation, work hardens the metal to impart increased strength in thecritical area. Further, as is best depicted in FIG. 9, the metal at theinternal wall of the hex depression is displaced outwardly of the pathof the threading tap, ergo only partial, if any, thread is formed in thedepression and consequently there is negligible weakening of the walladjacent the web. Still further, and perhaps most significant, is thefact that the internal hex depression provides positive driving faces inthe inner nut barrel adjacent the web, which faces oppose and match thehex wrenching faces on the outer barrel and thus reduce the torsionalstrain on the barrel connecting web incident to ultimate tightening.

Having considered the foregoing detailed description, one who now refersback to the United-Carr Fastener (hereinafter called UCF) Patent andHeller US. Pat. No. 2,851,079 earlier mentioned will readily recognizethe improvements in the art which are the contribution of the presentdisclosure and in which invention is seen to abide.

In the UCF teaching, which discloses a double barreled, sheet metal nutin the assembly, there exists an obvious lack of any upper supporting orbearing element for the portion 9 of the washer 6. Further, theconnecting elements of the nut and washer intersect at substantiallyright angles and relatively sharp corners which provide possibleimpediments to independent rotation or potential increased frictionalresistance to turning of the nut. Another important aspect of thepresent invention which is best understood by a comparison with the UCFdisclosure is that a substantial narrowing of the space between theinner and outer barrel portions even to the point that they areabutting, as is frequently the case with larger size nuts requiringthicker material and an enlarged inner barrel, has no adverse affect onthe nut to washer connection or the relative free spinning capabilitiesof the present components, whereas a similar narrowing of the spacingbetween the inner and outer barrels in UCF would cause a rotationinhibiting, jamming or binding of the washer portion 9. Obviously, itfollows that the required spacing which must be maintained in the UCFnut gives rise to increased production costs by reason of the additionalstock which must be used in fabricating larger sized nuts to be coupledto the washer in the manner disclosed therein.

The Heller US. Pat. No. 2,851,079 disclosure of a single walled sheetmetal nut with a single helix thread form is also considered deficientin that the assembly I lacks any bearing ring or other upper support forthe tubular portion 32 of the washer. Further, the Heller nut to washerconnection certainly does not recommend itself for use with a doublebarreled nut of the present type in that excessively wide spacingbetween the nut barrels would be required to receive the preflared endof the tubular washer portion 32, or a swaging or flaring tool whichwould have to pass between the nut barrels to curl the washer over thedimple 36 of the nut if the washer were first inserted in a perfectlytubular condition.

The reader, who should now have a clear understanding of the merits ofthe present disclosure, should proceed to refer to the claims whichfollow for a more precise definition of the scope of the inventionprotected by these Letters Patent.

We claim:

1. A sheet metal nut comprising an inner, threaded barrel portion, andan outer barrel portion joined to one end of said inner barrel portionthrough a connecting web, said outer barrel portion being disposed in atleast partially spaced, circumscribing relationship to said inner barrelportion, said outer barrel portion having an external polygonalconfiguration and thus presenting a plurality of wrenching faces, theend of said inner barrel portion proximate said one end and saidconnecting web having a polygonal depression of limited axial extentformed therein and presenting a plurality of internal faces opposite toand matching the said wrenching faces, said polygonal section of saidinner barrel portion being effective to transmit torque from said outerbarrel portion to said inner barrel portion when said nut is turned ontoa mating bolt with a tool engaging the said wrenching faces and therebyto reduce the torsional strain on said connecting web incident to thetightening of said nut onto a bolt.

2. A sheet metal nut according to claim 1, wherein said outer barrelportion has a peripheral bearing flange extending laterally outwardlyfrom its end opposite said one end.

3. A sheet metal nut according to claim 1 wherein the section of saidinner barrel portion having said polygonal depression formed thereincarries less than a full depth thread relative to a remainder of threadon said inner barrel portion.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,796,123 Dated March 12, 1974 Inventor(s) William B Duffy etal It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 64; after "(W. Stern)" delete "and" and insert a comma.Column 4, line 7, "Wit" should read with line 23, "roller" should readcollar line 25, "cured" should read curled Signed and sealed this 24thday of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents DO-1050 uscoMv-oc 60376-P69 .5. GOVIRNMENT PR|NT|NG OFFICE:

1. A sheet metal nut comprising an inner, threaded barrel portion, andan outer barrel portion joined to one end of said inner barrel portionthrough a connecting web, said outer barrel portion being disposed in atleast partially spaced, circumscribing relationship to said inner barrelportion, said outer barrel portion having an external polygonalconfiguration and thus presenting a plurality of wrenching faces, theend of said inner barrel portion proximate said one end and saidconnecting web having a polygonal depression of limited axial extentformed therein and presenting a plurality of internal faces opposite toand matching the said wrenching faces, said polygonal section of saidinner barrel portion being effective to transmit torque from said outerbarrel portion to said inner barrel portion when said nut is turned ontoa mating bolt with a tool engaging the said wrenching faces and therebyto reduce the torsional strain on said connecting web incident to thetightening of said nut onto a bolt.
 2. A sheet metal nut according toclaim 1, wherein said outer barrel portion has a peripheral bearingflange extending laterally outwardly from its end opposite said one end.3. A sheet metal nut according to claim 1 wherein the section of saidinner barrel portion having said polygonal depression formed thereincarries less than a full depth thread relative to a remainder of threadon said inner barrel portion.